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sudo hello

#sudo   #sudoers   #nopasswd   #visudo  

Table of Content

sudo hello#

Sudo is acronym for SuperUser DO Is allow user access restricted files and operations without logging as root user.

sudo is a tool install by default on ubuntu system

sudoers#

/etc/sudoers file contain sudo rule and configurations

[username] [any-hostname]=([run-as-username]:[run-as-groupname]) [commands-allowed]

Tip

Add rule to group sudo and not to specific user

edit#

To edit sudoers file we use the visudo command, The command validate the file before saving,

visudo prompt

  • e: edit

nopasswd#

To grant the permission to run commands as root users without the need of entering the password, set the following line sudoers file. 

%sudo   ALL=(ALL:ALL) NOPASSWD: apt update

demo#

Add rule for user that assign to sudo group to run apt update without password

before
sudo -l
Matching Defaults entries for user on lap2:
    env_reset, mail_badpass,
    secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin, use_pty

User user may run the following commands on lap2:
    (ALL : ALL) ALL

edit sudoers#

mk-!!! tip Command must be in full path 

which apt
/usr/bin/apt


sudo visudo

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL
%sudo   ALL=(ALL:ALL) NOPASSWD: /usr/bin/apt

check user privilege#

sudo -l
Matching Defaults entries for user on lap2:
    env_reset, mail_badpass,
    secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin, use_pty

User user may run the following commands on lap2:
    (ALL : ALL) ALL
    (ALL : ALL) NOPASSWD: /usr/bin/apt

Test#

  • kill current user session
  • run apt update the command sitl need to run with sudo
sudo -k
sudo apt update

demo II (using /etc/sudoers.d)#

The last line in sudoers file @includedir /etc/sudoers.d run rules defined in this folder

echo “%sudo ALL=(ALL:ALL) NOPASSWD: /usr/bin/apt” | sudo tee /etc/sudoers.d/apt

Warning

the visudo command is the recommended way to update sudoers content, since it protects against many failure modes

demo#

Add rule for user that assign to sudo group to mount tmpfs without switch to root and root password

run visudo to edit /etc/sudoers file

visudo tips

Command if visudo found error in sudoers file - e: edit

%sudo   ALL=(ALL:ALL) NOPASSWD: /usr/bin/mount -t tmpfs -o size=10m tmpfs /mnt/ramfs
  • list user privileges
    sudo -l
#
...

User user may run the following commands on lap2:
    (ALL : ALL) ALL
    (ALL : ALL) NOPASSWD: /usr/bin/mount -t tmpfs -o size\=10m tmpfs /mnt/ramfs
kill current sudo session
sudo -k